BHAI GURDAS INSTITUTE OF ENGG. AND TECH.

SANGRUR

REPORT OF6-MONTHS INDUSTRIAL TRAINNING

ON

EMBEDDED SYSTEMS

Submitted By : Submitted To :Ramandeep Singh Mr. Harsimran Singh40204020 HOD

DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING

BGIETSANGRUR

ACKNOWLEDGEMENT

Training is an agglomeration of the theoretical and practical and

technical concepts, which enhances our skills in the filed of technology.

Training plays a strong role in the building up of strong personality.

Training at SILICON TECHNICAL INSTITUTE is a learning experience.

I would like to thank SILICON for providing us the opportunity to carry

out my industrial training. It is a wonderful experience working with

learned people of the institute.

I am extremely thankful to Mr. Sanjay Arora (Head of training

department) for allowing us to carry on my training at this prestigious

organization. I am extremely indebted to him for allowing us to train

myself in various processes carried out in institute and helping me to do

my job properly.

I feel duty bound to express my sincere token of gratitude to Mr. Daljit

Singh and Mr.Harjeet Singh for their excellent expert guidance,

motivation and all the help, which has powered me to here today. They

explained the technicalities to me, which will remain of great help to me

in times to come.

I express my gratitude to all the employees for their immense support

and cooperation.

I am also thankful to those to whom I have forgotten to mention.

Ramandeep Singh

40204020

PREFACE

Training is an agglomeration of the theoretical and practical and

technical concepts, which enhances our skills in the field of technology.

Training plays a strong role in the building up of strong personality.

Training at Silicon technical institute is a learning experience.

The training report has been developed as a part of the industrial

training that Punjab technical university (Punjab) requires its students to

undergo after the sixth semester of the curriculum the purpose of the

industrial training is to familiarize the students of the Bachelor or

engineering course with the present working environment in the country.

To provide them to study with the latest trends those have been

established and edged a well as the one’s that are being developed in

the country. Moreover to make students feel sure that whatever they are

learning in this training period would certainly help them for the future

courses of action and help them to develop their potential and technical

skills.

To allow them to explore various fields and to better equip them as a

professional in the time to time.

The training is being carried out at Silicon Technical Institute is an

education centre for course of Embedded System situated at

Chandigarh, Sector -35C. It’s a perfect institute for the persons want to

shape their career.

TABLE OF CONTENTS

1) Company Profile ……………………………………………1 - 4

2) Introduction to Electronic Devices ………………………5 - 45

3) Introduction to Logic Gates ……………………………46 - 52

4) Introduction to Embedded Systems ………………….52 – 117

Micro-controller 8051

Interfacing of Various Devices

5) Software Description …………………………………..118 - 126

Introduction to Kiel.

Commands used.

Introduction to ISP.

6) Some Basic programs using assembly 127-130

SILICON TECHNICAL INSTITUTE

SILICON is a well established institute in Chandigarh with an experience of

fifteen years and has gained recognition as training organization of high repute

offering international quality education in the field of Electronics &

Communication technology. The centre boasts of a professional faculty which

satisfies the needs & expectancy of today's knowledge hungry students.

Our Institute provides training to the engineering students which generally

colleges recommend after completion of 4th, 6th & last semester. The training

programs are of two months, three months, & six months duration and 100%

practical oriented in Electronics, Telecommunication & Computers,

UNIQUE FEATURES

• 100% practical oriented approach.

• Instill creativity in students.

• Latest hardware & software technology.

• High quality education with latest curriculum & strong fundamentals.

• Optimum utilization of hardware/software, manpower and office space,

hence maximum turnover. Extensive preparation & innovative techniques.

• Extensive preparation & innovative techniques.

ELECTRONIC DEVICES

An electronic component is any indivisible electronic building block packaged

in a discrete form with two or more connecting leads or metallic pads.

Components are intended to be connected together, usually by soldering to a

printed circuit board, to create an electronic circuit with a particular function

(for example an amplifier, radio receiver, or oscillator). Components may be

packaged singly (resistor, capacitor, transistor, diode etc.) or in more or less

complex groups as integrated circuits (operational amplifier, resistor array,

logic gate etc). Active components are sometimes called devices rather than

components.

ELECTRICAL RESISTANCE:

Electrical resistance is a measure of the degree to which an object opposes the

passage of an electric current. The Sl unit of electrical resistance is the ohm,

The quantity of resistance in an electric circuit determines the amount of

current flowing in the circuit for any given voltage applied to the circuit.

R=V / I

where

R is the resistance of the object, usually measured in ohms, equivalent to

J.s/C2

V is the potential difference across the object, usually measured in volts

/ is the current passing through the object, usually measured in amperes

Resistors are two-terminal devices that restrict, or resist, the flow of current.

The larger the resistor, the less current can flow through it for a given voltage

(an equation known as Ohm's law, V=113, relates current, resistance, and

voltage). Electrical resistance within the resistor body is caused by the

collisions of electrons in motion through the resistor. Such collisions cause

energy to be dissipated in the form of heat or light (as in a toaster or light bulb).

Resistance is measured in Ohms - a 1 Ohm resistor is relatively small, and a

100KOhm resistor is relatively large. Resistors find many uses in electronic

systems, On the Digilab board, resistors are used to limit the current that flows

into an output LED (so they don't burn too bright and destroy themselves) and

to limit the current that flows in response to a button or switch input being

activated. The Digilab board uses several different resistor values. Of course,

the correct resistor must be loaded in the correct place on the PCB.

Resistors come in many shapes and sizes, and depending on their size and

construction technology, they can dissipate differing amounts of power (the

amount of power dissipated in a resistor can be calculated using the equation

P=I 2 R, where I is the current flowing through the resistor and R is the

resistance). Typically, resistors used in digital systems encounter relatively low

voltages and currents, and therefore, they can be relatively small. The Digilab

resistors are rated to dissipate 250mW of power, or 1/4 Watt. Resistors that can

dissipate more than 1/4 Watt are physically larger. For example, power

resistors that can dissipate several Watts or more can be cigar-sized or even

larger. For small resistors, resistor values are "encoded" as a series of coloured

bands on the resistor body.

To determine the value of a small resistor (i.e., 1/8 Watt or 1/4 Watt), first

locate the tolerance band on one end of the resistor - it will typically be either

gold (59% tolerance) or silver (10% tolerance). The colour band at the other

end of the resistor is band1. Use the table below to find the two-digit number

associated with the colors of bands 1 and 2. The band nearest the tolerance

band is the multiplier (or exponent) band - the digits associated with the first

two colour bands are multiplied by 10 raised to the power indicated by the

colour of the multiplier band. The following table associates band colors to

digits and multiplier factors. Simply multiply the two-digit value by the

multiplier, and you’ve got the resistor value.

BAND

COLOR

1st and 2nd band

digits

Multiplier Tolerance

Resistor schematic

symbol

Black 0 100 1%

Brown 1 101 2%

Red 2 102 3%

Orange 3 103 4%

Yellow 4 104 N/A

Green 5 105 N/A

Blue 6 106 N/A

Violet 7 107 N/A

Grey 8 108 N/A

White 9 109 N/A

Gold N/A .1 5%

Silver N/A .01 10%

No color N/A N/A 20%

Resistors are manufactured with many body colors, with tan or light brown

being the most typical. The only significant resistor body colors are white and

blue; these colors signify a non-flammable or fusible resistor. Such resistors are

used in circuits where overheating might pose a safety risk. In circuit

schematics and in parts lists, resistor reference designators always begin with

an "R". You can see several rectangular white boxes with "R-" on the Digilab

board silk-screen. The schematic symbol for a resistor is shown above.

Resistors are non-polarised, so they can be placed in a PCB in any orientation.

For a wide variety of materials and conditions, the electrical resistance does not

depend on the amount of current flowing or the amount of applied voltage. V

can either be measured directly across the object or calculated from a

subtraction of voltages relative to a reference point. The former method is

simpler for a single object and is likely to be more accurate. There may also be

problems with the latter method if the voltage supply is AC and the two

measurements from the reference point are not in phase with each other.

RESISTANCE IN SERIES AND PARALLEL CIRCUITS

Series circuits

A series circuit is a circuit in which resistors are arranged in a chain, so

the current has only one path to take. The current is the same through

each resistor. The total resistance of the circuit is found by simply

adding up the resistance values of the individual resistors:

equivalent resistance of resistors in series : R = R1 + R2 + R3 + ...

A series circuit is shown in the diagram above.

With a 10 V battery, by V = I R the total current in the circuit is:

I = V / R = 10 / 20 = 0.5 A. The current through each resistor would be

0.5 A.

PARALLEL CIRCUITS

A parallel circuit is a circuit in which the resistors are arranged with their

heads connected together, and their tails connected together. The

current in a parallel circuit breaks up, with some flowing along each

parallel branch and re-combining when the branches meet again. The

voltage across each resistor in parallel is the same.

The total resistance of a set of resistors in parallel is found by adding up

the reciprocals of the resistance values, and then taking the reciprocal

of the total:

Equivalent resistance of resistors in parallel: 1 / R = 1 / R1 + 1 / R2 + 1 /

R3 +...

A parallel circuit is shown in the diagram above. In this case the current

supplied by the battery splits up, and the amount going through each

resistor depends on the resistance. If the values of the three resistors

are:

With a 10 V battery, by V = I R the total current in the circuit is: I = V / R

= 10 / 2 = 5 A.

The individual currents can also be found using I = V / R. The voltage

across each resistor is 10 V, so:

I1 = 10 / 8 = 1.25 A

I2 = 10 / 8 = 1.25 A

I3=10 / 4 = 2.5 A

Note that the currents add together to 5A, the total current.

A parallel resistor short-cut

If the resistors in parallel are identical, it can be very easy to work out

the equivalent resistance. In this case the equivalent resistance of N

identical resistors is the resistance of one resistor divided by N, the

number of resistors. So, two 40-ohm resistors in parallel are equivalent

to one 20-ohm resistor; five 50-ohm resistors in parallel are equivalent

to one 10-ohm resistor, etc.

When calculating the equivalent resistance of a set of parallel resistors,

people often forget to flip the 1/R upside down, putting 1/5 of an ohm

instead of 5 ohms, for instance. Here's a way to check your answer. If

you have two or more resistors in parallel, look for the one with the

smallest resistance. The equivalent resistance will always be between

the smallest resistance divided by the number of resistors, and the

smallest resistance. Here's an example.

You have three resistors in parallel, with values 6 ohms, 9 ohms, and 18

ohms. The smallest resistance is 6 ohms, so the equivalent resistance

must be between 2 ohms and 6 ohms (2 = 6 /3, where 3 is the number

of resistors).

Doing the calculation gives 1/6 + 1/12 + 1/18 = 6/18. Flipping this upside

down gives 18/6 = 3 ohms, which is certainly between 2 and 6.

CAPACITORS

A capacitor is an electrical device that can store energy in the electric field

between a pair of closely-spaced conductors (called 'plates). When voltage is

applied to the capacitor, electric charges of equal magnitude, but opposite

polarity, build up on each plate.

A capacitor is a two-terminal device that can store electric energy in the form

of charged particles. You can think of a capacitor as a reservoir of charge that

takes time to fill or empty. The voltage across a capacitor is proportional to the

amount of charge it is storing - since it is not possible to instantaneously move

charge to or from a capacitor, it is not possible to instantaneously change the

voltage across a capacitor. It is this property that makes capacitors useful on the

Digilab board.

Capacitance is measured in Farads - a one Farad capacitor can store one

Coloumb of charge at one volt. For engineering on a small scale (i.e.,

hand-held or desk-top devices), a one Farad capacitor stores far too much

charge to be of general use (it would be like a car having a 1000 gallon gas

tank). More useful capacitors are measured in micro-farads (uF) or pico-farads

(pF). The terms "milli-farad" and "nano-farad" are rarely used. Large capacitors

often have their value printed plainly on them, such as "10 uF (for 10

microfards). Smaller capacitors, appearing as small disks or wafers, often have

their values printed on them in an encoded manner (similar to the resistor packs

discussed above). For these capacitors, a three digit number indicates the

capacitor value in Pico farads. The first two digits provides the "base" number,

and the third digit provides an exponent of 10 (so, for example, "104" printed

on a capacitor indicates a capacitance value of 10 x 10 4 or 100000 pF).

Occasionally, a capacitor will only show a two digit number, in which case that

number is simply the capacitor value in pF. (To be complete, if a capacitor

shows a three digit number and the third digit is 8 or 9, then the first two digits

are multiplied by .01 and .1 respectively). Often, a single letter is appended to

the capacitance value -this letter indicates the quality of the capacitor.

Capacitors are used on the Digilab board to keep the voltage supplies and some

signals stable regardless of circuit activity, and to store charge when inputs are

activated in order to slow their assertion times. Twenty-seven capacitors of

three different types and values are used on the Digilab board. The majority of

the capacitors (24 out of 27) are used to decouple Digilab's integrated circuits

from the power supply. These 24 bypass capacitors are placed on the board

very close to the Vdd pins of all chips, where they can supply the short-term

electrical current needs of the chips. Without such bypass capacitors, individual

chips could cause the Vdd supply across the entire Digilab board to dip below

5V during times of heavy current demand. Nearly every chip in every digital

system uses bypass capacitors. Bypass capacitor value can be determined if the

worst-case current requirements are known (by using the formula I = C dv/dt),

but more typically, capacitors in the range 0.01uF to 0.1uF are used without

regard to the actual current requirements. The Digilab board uses 0.047uF

bypass capacitors. The board also uses a bulk bypass capacitor (C27) to

provide charge storage for the entire circuit board - this large 47uF capacitor

can supply the individual bypass capacitors during times of exceptional need.

ENERGY STORAGE

A capacitor can store electric energy when disconnected from its charging

circuit, so it can be used like a temporary battery. Capacitors are common used

in electronic devices to maintain power supply while batteries are being

changed. (This prevents loss of information in volatile memory.)

Capacitors are used in power supplies where they smooth the output of a full or

half wave rectifier. They can also be used in charge pump circuits as the energy

storage element in the generation of higher voltages than the input voltage,

Capacitors are connected in parallel with the power circuits of most electronic

devices and larger systems (such as factories) to shunt away and conceal

current fluctuations from the primary power source to provide a "clean" power

supply for signal or control circuits. Audio equipment, for example, uses

several capacitors in this way, to shunt away power line hum before it gets into

the signal circuitry. The capacitors act as a local reserve for the DC power

source, and bypass AC currents from the power supply. This is used in car

audio applications, when a stiffening capacitor compensates for the inductance

and resistance of the leads to the lead-acid car battery.

CAPACITORS IN SERIES

The total capacitance of the above circuit is:

CAPACITORS IN PARALLEL

The total capacitance of this circuit will be:

Ceq = C1 + C2 + ….. + Cn

CAPACITOR TYPES

Metal film: Made from high quality polymer foil (usually

polycarbonate, polystyrene, polypropylene, polyester (Mylar), and for

high quality capacitors polysulfone), with a layer of metal deposited on

surface. They have good quality and stability, and are suitable for timer

circuits. Suitable for high frequencies.

Mica: Similar to metal film. Often high voltage. Suitable for high

frequencies. Expensive.

Paper: Used for high voltages

Glass: Used for high voltages. Expensive. Stable temperature

coefficient in a wide range of temperatures.

Ceramic: Chips of altering layers of metal and ceramic. Depending on

their dielectric, whether Class 1 or Class 2, their degree of

temperature/capacity dependence varies. They often have (especially the

class 2) high dissipation factor, high frequency coefficient of dissipation,

their capacity depends on applied voltage, and their capacity changes

with aging. However they find massive use in common low-precision

coupling and filtering applications. Suitable for high frequencies.

Electrolytic: Polarized. Construction ally similar to metal film, but the

electrodes are made of aluminum etched to acquire much higher

surfaces, and the dielectric is soaked with liquid electrolyte. They suffer

from high tolerances, high instability, gradual loss of capacity especially

when subjected to heat, and high leakage. Special types with low

equivalent series resistance are available. Tend to lose capacity in low

temperatures. Can achieve high capacities.

Tantalum: Like electrolytic. Polarized. Better performance with higher

frequencies. High dielectric absorption. High leakage. Have much better

performance in low temperatures.

Supercapacitrs: Made from carbon aerogel, carbon nanotubes, or

highly porous electrode materials. Extremely high capacity. Can be used

in some applications instead of rechargeable batteries.

USES OF CAPACITORS

Capacitors are used for several purposes:

Timing - for example with a 555 timer IC controlling the charging and

discharging.

Smoothing - for example in a power supply.

Coupling - for example between stages of an audio system and to

connect aloudspeaker.

Filtering - for example in the tone control of an audio system.

Tuning - for example in a radio system.

Storing energy - for example in a camera flash circuit

CURRENT

Electric current Is by definition the flow of electric charge. The Sl unit of

blectric current Is the ampere (A), which Is equal to a flow of one coulomb of

charge per second.

VOLTAGE

Voltage is the difference of electrical potential between two points of an

electronic circuit, expressed in volts [1]. It measures the capacity (not the

technical meaning) of an electric field to cause an electric current in an

electrical conductor. Depending on the difference of electrical potential it is

called extra low voltage, low voltage, high voltage or extra high voltage

RESISTANCE

Electrical resistance is a measure of the degree to which an object opposes the

passage of an electric current. The SI unit of electrical resistance is the ohm.

OHM'S LAW

Ohm's law predicts the current in an (ideal) resistor (or other ohmic device) to

be applied voltage divided by resistance:

I=V/R

Where

/is the current, measured in amperes

V is the potential difference measured in volts

R is the resistance measured in ohms

MEASURING INSTRUMENTS

VOLTMETER

A voltmeter is an instrument used for measuring the potential difference

between two points in an electric circuit.

The voltage can be measured by allowing it to pass a current through a

resistance; therefore, a voltmeter can be seen as a very high resistance

ammeter. One of the design objectives of the instrument is to disturb the circuit

as little as possible and hence the instrument should draw a minimum of

electric current to operate. This is achieved by using a sensitive ammeter or

micrometer in series with a high resistance.

The moving coil galvanometer is one example of this type of voltmeter. It

employs a small coil of fine wire suspended in a strong magnetic field. When

an electrical current is applied, the galvanometer's indicator rotates and

compresses a small spring. The angular rotation is proportional to the current

that is flowing through the coil- For use as a voltmeter, a series resistance is

added so that the angular rotation becomes proportional to the applied voltage

AMMETER

An ammeter is a measuring instrument used to measure the flow of electric

current in a circuit. Electric currents are measured in amperes, hence the name.

The word "ammeter" is commonly misspelled or mispronounced as

"ampmeter" by some.

The earliest design is the D'Arsonval galvanometer or moving coil ammeter. It

uses magnetic deflection, where current passing through a coil causes the coil

to move in a magnetic field. The voltage drop across the coil is kept to a

minimum to minimize resistance across the ammeter in any circuit into which

the it is inserted.

Moving iron ammeters use a piece or pieces of iron which move when acted

upon by the electromagnetic force of a fixed coil of (usually heavy gauge) wire.

This type of meter responds to both direct and alternating currents (as opposed

to the moving coil ammeter, which works on direct current only).

To measure larger currents, a resistor called a shunt is placed in parallel with

the meter. Most of the current flows through the shunt, and only a small

fraction flow through the meter. With this solution, arbitrarily large currents

can be measured with a single meter. Traditionally, the meter used with a shunt

reaches full-scale deflection when a voltage of 50mV is placed across its coil,

so shunts are typically designed to produce a voltage drop of 50mV when

carrying their full rated current.

More modern ammeter designs are non-mechanical, or digital, and use an

analog to digital converter to measure the voltage across the shunt resistor. The

ADC is read by a microcomputer that performs the calculations to display the

current through the resistor.

One problem with the use of an ammeter is the need for the meter to be inserted

into the circuit and become part of it. Mistakenly placing the ammeter in

parallel with a circuit will blow the fuse, possibly damaging the meter and

causing injury. In AC circuits, an inductive coupling adapter converts the

magnetic field around a conductor into a small AC current that can be easily

read by a meter. See clamp meter. In a similar way, accurate DC non-contact

arnmeters have been constructed using Hall effect magnetic field sensors

OHMMETER

An Ohmmeter is an electrical measuring instrument that measures electrical

resistance, the opposition to the flow of an electric current.

The original design of an ohmmeter provided a small battery to apply a voltage

to a resistance. It used a galvanometer to measure the electric current through

the resistance. The scale of the galvanometer was marked in ohms, because the

fixed voltage from the battery assured that as resistance decreased, the current

through the meter would increase.

A more accurate type of ohmmeter has an electronic circuit that passes a

constant current I through the resistance, and another circuit that measures the

voltage V across the resistance. According to the following equation, derived

from Ohm's Law, the value of the resistance R is given by:

R= V/1

For high-precision measurements the above types of meter are inadequate, This

is because the meter's reading is the sum of the resistance of the measuring

leads, the contact resistances and the resistance being measured. To reduce this

effect, a precision ohmmeter has four terminals, called Kelvin contacts. Two

terminals carry the current from the meter, while the other two allow the meter

to measure the voltage across the resistor. With this type of meter, any current

drop due to the resistance of the first pair of leads and their contact resistances

is ignored by the meter. This four terminal measurement technique is called

Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin

bridge in 1861 to measure very low resistances.

DIODES

Diodes are constructed from the same type of silicon as transistors, but they are

simpler devices that have only two terminals. Called the anode and cathode, the

two ends of the diode are constructed of positively doped silicon (the anode)

joined directly to negatively doped silicon (the cathode). This pn-junction

exhibits the unique characteristic of allowing current to flow in only one

direction (from the anode to the cathode). Diodes have a minimum threshold

voltage (or Vth, usually around 0.7V) that must be present between the anode

and cathode in order for current to flow. If the anode voltage is not at least Vth

greater than the cathode voltage, no current will flow. Likewise, if the cathode

voltage is greater than the anode voltage, the diode is said to be reverse-biased

and no current will flow. In an ideal diode, if the diode voltage equals the

threshold voltage (plus a small amount), then unlimited current can flow

without causing the voltage across the diode to increase. And, if the diode is

reversed-biased, no current will flow regardless of reverse-voltage magnitude.

Diodes

Diodes have many uses in electronic circuits. As examples, they are frequently

employed in power supply circuits to turn alternating current (AC) into direct

current (DC), they are used to limit the amount of over-voltage that can be

applied to a given circuit node, and they are used to force given circuit nodes to

remain at or below a certain voltage. On the Digilab board, three individual

diodes are used to limit the voltages applied to the Red, Blue, and Green pins

of the VGA connector (M) to 0.7VDC or less.

Note the identification methods used to mark a diode's cathode -terminal: the

schematic symbol has a line at the point of the triangle; the physical diode has a

dark line on the plastic component housing; and the silk-screen pattern has both

a line at the cathode end and a square pad for the cathode lead. When loading a

diode into a circuit board, make sure that the dark line on the diode matches the

line in the silk-screen pattern. Remember that since diodes allow current to

flow in only one direction, a backwards diode will cause the circuit to

malfunction.

LED SCHEMATIC SYMBOL

Diodes locations on the circuit board are typically denoted with a "D-"

reference designator

A light-emitting diode (LED) is a semiconductor device that emits incoherent

narrow-spectrum light when electrically biased in the forward direction. This

effect is a form of electro luminescence. The color of the emitted light depends

on the composition and condition of the semi conducting material used, and

can be infrared, visible or near-ultraviolet. Rubin Braunstein of the Radio

Corporation of America first reported on infrared emission from gallium

arsenide (GaAs) and other semiconductor alloys in 1955. Experimenters at

Texas Instruments, Bob Biard [1] and Gary Pittman, found in 1961 that gallium

arsenide gave off infrared (invisible) light when electric, current was applied.

Biard and Pittman were able to establish the priority of their work and received

the patent for the infrared lightemitting diode. Nick Holonyak Jr. of the General

Electric Company developed the first practical visible-spectrum LED in 1962.

LEDs are available in a wide variety of sizes and shapes. The 'standard' LED

has a round cross-section of 5mm diameter and this is probably the best type

for general use, but 3mm round LEDs are also popular.

Round cross-section LEDs are frequently used and they are very easy to install

on boxes by drilling a hole of the LED diameter, adding a spot of glue will help

to hold the LED if necessary. LED clips are also available to secure LEDs in

holes. Other cross-section shapes include square, rectangular and triangular.

As well as a variety of colours, sizes and shapes, LEDs also vary in their

viewing angle. This tells you how much the beam of light spreads out. Standard

LEDs have a viewing angle of 600 but others have a narrow beam of 300 or

less.

Rapid Electronics stock a wide selection of LEDs and their catalogue is a good

guide to the range available.

ADVANTAGES OF USING LEDS

LEDs produce more light per Watt than do incandescent bulbs; this is

useful in battery powered devices.

LEDs can emit light of an intended color without the use of color filters

that traditional lighting methods require. This is more efficient and can

lower initial costs.

The solid package of an LED can be designed to focus its light.

Incandescent and fluorescent sources often require an external reflector

to collect light and direct it in a usable manner.

When used in applications where dimming is required, LEDs do not

change their colour tint as the current passing through them is lowered,

unlike incandescent lamps, which yellow.

LEDs are built i1nside solid cases that protect them, unlike incandescent

and discharge sources, making them extremely durable.

LEDs have an extremely long life span: upwards of 100,000 hours,

twice as long as the best fluorescent bulbs and twenty times longer than

the best incandescent bulbs. (Incandescent bulbs can also be made to last

an extremely long time by running at lower than normal voltage, but

only at a huge cost in efficiency; LEDs have a long life when operated at

their rated power.)

Further, LEDs mostly fail by dimming over time, rather than the abrupt

burn-out of incandescent bulbs,

LEDs light up very quickly. A typical red indicator LED will achieve

full brightness in microseconds; LEDs used in communications devices

can have even faster response times.

LEDs can be very small and are easily populated onto printed circuit

boards.

Connecting LEDs in series

If you wish to have several LEDs on at the same time it may be possible to

connect them in series. This prolongs battery life by lighting several LEDs with

the same current as just one LED.

All the LEDs connected in series pass the same current so it is best if they

are all the same type. The power supply must have sufficient voltage to

provide about 2V for each LED (4V for blue and white) plus at least another

2V for the resistor. To work out a value for the resistor you must add up all the

LED voltages

SIZE AND SHAPES

LEDs are produced in a staggering array of shapes and sizes, The 5 mm

cylindrical package (red, fifth from the left) is the most common, estimated at

80% of world production. The color of the plastic lens is often the same as the

actual color of light emitted, but not always. For instance, purple plastic is

often used for infrared LEDs, and most blue devices have clear housings. There

are also LEDs in extremely tiny packages, such as those found on blinkies.

Colours of LEDs

LEDs are available in red, orange, amber, yellow, green, blue and white. Blue

and white LEDs are much more expensive than the other colors.

The color of an LED is determined by the semiconductor material, not by the

coloring of the 'package' (the plastic body). LEDs of all colors are available in

uncolored packages which may be diffused (milky) or clear (often described as

I water clear'). The colored packages are also available as diffused (the

standard type) or transparent

LIST OF LED APPLICATIONS

Some of these applications are further elaborated upon in the following text.

Architectural lighting.

Status indicators on all sorts of equipment.

Traffic lights and signals.

Exit signs.

Motorcycle and Bicycle lights.

Toys and recreational sporting goods.

Railroad crossing signals.

Light bars on emergency vehicles.

Elevator Push Button Lighting.

Thin, lightweight message displays at airports and railway stations and

as destination displays for trains, buses, trams and ferries.

Red or yellow LEDs are used in indicator and alphanumeric displays in

environments where night vision must be retained: aircraft cockpits,

submarine and ship bridges, astronomy observatories, and in the field,

e.g. night time animal watching and military field use.

Red, yellow, green, and blue LEDs can be used for model railroading

applications.

Remote controls, such as for TVs and VCRs, often use infrared LEDs.

In dot matrix arrangements for displaying messages.

Glow lights, as a more expensive but longer lasting and reusable

alternative to Glow sticks.

Movement sensors, for example in optical computer mice.

Because of their long life and fast switching times, LEDs have been

used for automotive high-mounted brake lights and truck and bus brake

lights and turn signals for some time, but many high-end vehicles are

now starting to use LEDs for their entire rear light clusters. Besides the

gain in reliability, this has styling advantages because LEDs are capable

of forming much thinner lights than incandescent lamps with parabolic

reflectors. The significant improvement in the time taken to light up

(perhaps 0.5s faster than an incandescent bulb) improves safety by

giving drivers more time to react.

Backlighting for LCD televisions and displays. The availability of LEDs

in specific colors (RGB) enables a full-spectrum light source which

expands the color gamut by as much as 45%.

New stage lighting equipment is being developed with LED sources in

primary red-green-blue arrangements.

LED phototherapy for acne using blue or red LEDs has been proven to

significantly reduce acne over a 3 month period.

As Voltage Reference in electronic circuits. The constant voltage drop

(e.g. 1.7 V for a normal red LED) can be used instead of a Zener diode

in low-voltage regulators. Zener diodes are not available below voltages

of about 3 V.

RELAY

A relay is an electrical switch that opens and closes under control of another

electrical circuit. In the original form, the switch is operated by an

electromagnet to open or close one or many sets of contacts. It was invented by

Joseph Henry in 1835. Because a relay is able to control an output circuit of

higher power than the input circuit, it can be considered, in a broad sense, to be

a form of electrical amplifier

OPERATION

When a current flows through the coil, the resulting magnetic field attracts an

armature that is mechanically linked to a moving contact. The movement either

makes or breaks a connection with a fixed contact. When the current to the coil

is switched off, the armature is returned by a force approximately half as strong

as the magnetic force to its relaxed position. Usually this is a spring, but gravity

is also used commonly in industrial motor starters. Most relays are

manufactured to operate quickly. In a low voltage application, this is to reduce

noise. In a high voltage or high current application, this is to reduce arcing.

If the coil is energized with DC, a diode is frequently installed across the coil,

to dissipate the energy from the collapsing magnetic field at deactivation,

which would otherwise generate a spike of voltage and might cause damage to

circuit components. If the coil is designed to be energized with AC, a small

copper ring can be crimped to the end of the solenoid. This "shading ring"

creates a small out-of-phase current, which increases the minimum pull on the

armature during the AC cycle. [1]

By analogy with the functions of the original electromagnetic device, a

solid-state relay is made with a thyristor or other solid-state switching device.

To achieve electrical isolation, a light emitting diode (LED) is used with a

photo transistor.

APPLICATIONS

Relays are used:

to control a high-voltage circuit with a low-voltage signal, as in some

types of modems,

to control a high-current circuit with a low-current signal, as in the

starter solenoid of an automobile,

to detect and isolate faults on transmission and distribution lines by

opening and closing circuit breakers (protection relays),

to isolate the controlling circuit from the controlled circuit when the two

are at different potentials, for example when controlling a

mains-powered device from a low-voltage switch. The latter is often

applied to co~trol office lighting as the low voltage wires are easily

installed in partitions, which may be often moved as needs change. They

may also be controlled by room occupancy detectors in an effort to

conserve energy,

to perform logic functions. For example, the boolean AND function is

realised by connecting NO relay contacts in series, the OR function by

connecting NO contacts in parallel. The change-over or Form C contacts

perform the XOR (exclusive or) function. Similar functions; for NAND

and NOR are accomplished using NC contacts. Due to the failure modes

of a relay compared with a semiconductor, they are widely used in

safety critical logic, such as the control panels of radioactive waste

handling machinery. -

ALTERNATING CURRENT

An alternating current (AC) is an electrical current whose magnitude and

direction vary cyclically, as opposed to direct current, whose direction remains

constant. The usual waveform of an AC power circuit is a sine wave, as this

result in the most efficient transmission of energy. However in certain

applications different waveforms are used, such as triangular or square waves.

Used generically, AC refers to the form in which electricity is delivered to

businesses and residences. However, audio and radio signals carried on

electrical wire are also examples of alternating current. In these applications, an

important goal is often the recovery of information encoded (or modulated)

onto the AC signal.

DIRECT CURRENT

Direct current (DC or "continuous current") is considered as the constant

flow of electrons in the single direction from low to high potential. This is

typically in a conductor such as a wire, but can also be through

semiconductors, insulators, or even through a vacuum as in electron or ion

beams. In direct current, the electric charges flow in the same direction,

distinguishing it from alternating current (AC). A term formerly used for direct

current was Galvanic current.

ALTERNATING VS. DIRECT CURRENT

So far we have been talking about a constant supply of voltage - one that

doesn't change over time, such as a battery before it starts to run down. This is

what is commonly know of as direct current or DC which is to say that there is

no change in voltage over a period of time. This is not the kind of electricity

found coming out of the sockets in your wall at home. The electricity supplied

by the hydro company changes over short periods of time (it changes over long

periods of time as well, but that's an entirely different story...) Every second,

the voltage difference between the two terminals in your wall socket fluctuates

between about -170 V and 170 V sixty times a second (if you live in North

America, at least ...). This brings up two important points to discuss.

Firstly, the negative voltage... All a negative voltage means is that the electrons

are flowing in a direction opposite to that being measured. There are more

electrons in the tested point in the circuit than there are in the reference point,

therefore more negative charge. If you think of this in terms of the two tanks of

water - if we're sitting at the bottom of the empty tank, and we measure the

relative pressure of the full one, its pressure will be more, and therefore

positive relative to your reference. If you're at the bottom of the full tank and

you measure the pressure at the bottom of the empty one, you'll find that it's

less than your reference and therefore negative. (Two other analogies to

completely confuse you.., it's like describing someone by their height. It doesn't

matter how tall or short someone is - if you say they're tall, it probably means

that they're taller than you.

Secondly, the idea that the voltage is fluctuating. When you plug your coffee

maker into the wall, you'll notice that the plug has two terminals. One is a

reference voltage which stays constant (normally called a "cold" wire in this

case ...) and one is the "hot" wire which changes in voltage realtive to the cold

wire. The device in the coffee maker which is doing the work is connected with

each of these two wires. When the voltage in the hot wire is positive in

comparison to the cold wire, the current flows from hot through the coffee

maker to cold. One one-hundred and twentieth of a second later the hot wire is

negative compared to the cold, the current flows from cold to hot. This is

commonly known as alternating current or AC.

So remember, alternating current means that both the voltage and the current

are changing in time.

DIGITAL ELECTRONICS

Digital electronics are those electronics systems that use a digital signal instead

of an analog signal. Digital electronics are the most common representation of

Boolean algebra and are the basis of all digital circuits for computers, mobile

phones, and numerous other consumer products.

The most common "fundamental unit" of digital electronics is the logic gate.

By combining numerous logic gates (from tens to hundreds of thousands) more

complex systems can be created. The complex system of digital electronics is

collectively referred to as a digital circuit.

To most electronic engineers, the terms "digital circuit", "digital system" and

"logic" are interchangeable in the context of digital circuits

ADVANTAGES

The usual advantages of digital circuits when compared to analog circuits

are,

Digital systems interface well with computers and are easy to control

with software. It is often possible to add new features to a digital system

without changing hardware, and to do this remotely, just by uploading

new software. Design errors or bugs can be worked-around with a

software upgrade, after the product is in customer hands.

Information storage can be much easier in digital systems than in analog

ones. In particular, the great noise-immunity of digital systems makes it

possible to store data and retrieve it later without degradation. In an

analog system, aging and wear and tear will degrade the information in

storage, but in a digital system, as long as the wear and tear is below a

certain level, the information can be recovered perfectly.

LOGIC LEVELS

A Boolean logical input or output always takes one of two logic levels, These

logic levels can go by many names Including: on / off, high (H) / low (L), one

(1) / zero (0), true (T) / false (F), positive / negative, positive / ground, open

circuit / close circuit, potential difference I no difference, yes / no. For

consistency, the names 1 and 0 will be used below

LOGIC GATE

A logic gate performs a logical operation on one or more logic inputs and

produces a single logic output. The logic normally performed is Boolean logic

and is most commonly found in digital circuits. Logic gates are primarily

implemented electronically using diodes or transistors, but can also be

constructed using electromagnetic relays, fluidics, optical or even mechanical

elements.

A logic gate is an elementary building block of a digital circuit. Most logic

gates have two inputs and one output. At any given moment, every terminal is

in one of the two binary conditions low (0) or high (1), represented by different

voltage levels. The logic state of a terminal can, and generally does, change

often, as the circuit processes data. In most logic gates, the low state is

approximately zero volts (0 V), while the high state is approximately five volts

positive (+5 V).There are seven basic logic gates: AND, OR, XDR, NOT,

NAND, NOR, and XNOR.

AND GATE

The AND gate is so named because, if 0 is called "false" and 1 is called "true,"

the gate acts in the same way as the logical "and" operator. The following

illustration and table show the circuit symbol and logic combinations for an

AND gate. (In the symbol, the input terminals are at left and the output

terminal is at right.) The output is "true" when both inputs are "true."

Otherwise, the output is "false."

Symbol

Input 1 Input 2 Output

0 0 0

0 1 0

1 0 0

1 1 1

OR GATE

The OR gate gets its name from the fact that it behaves after the fashion of the

logical inclusive "or." The output is "true" if either or both of the inputs are

"true." If both inputs are "false," then the output is "false."

Symbol

Input 1 Input 2 Output

0 0 0

0 1 1

1 0 1

1 1 1

NOT GATE

The NOT gate or inverter is a digital logic gate that implements logical

negation. It behaves according to the truth table to the right. A HIGH output (1)

results if the inputs is LOW (0). If the input is HIGH (1), a LOW output (0)

results.

Input Input

1 0

0 1

Symbol

NAND GATE

The NAND gate operates as an AND gate followed by a NOT gate. It acts in

the manner of the logical operation "and" followed by negation. The outputis

"false" if both inputs are "true." Otherwise, the output is "true."

Symbol

Input 1 Input 2 Output

0 0 1

0 1 1

1 0 1

1 1 0

NOR GATE

The NOR gate is a combination OR gate followed by an inverter, its output is

“true” if both inputs are “false”. Otherwise, the output is “false.”

NOR gate

Input 1 Input 2 Output

0 0 1

0 1 0

1 0 0

1 1 0

XNOR GATE

The XNOR (exclusive-NOR) gate is a combination XOR gate following by an

inverter. Its output is “true” if inputs are the same, and “false” if the inputs are

different.

Input 1 Input 2 Output

0 0 1

0 1 0

1 0 0

1 1 1

Using combinations of logic gates, complex operations can be performed. In

theory, there is no limit to the number of gates that can be arrayed together in a

single device. But in practice, there is a limit to the number of gates that can be,

packed into a given physical space. Arrays of logic gates are found in digital

integrated circuits (ICs). As IC technology advances, the required physical

volume for each individual logic gate decreases and digital devices of the same

or smaller size become capable of performing ever-more-complicated

operations at ever-increasing speeds.

INTRODUCTION TO EMBEDDED SYSTEMA specialized computer system. that is part of a larger

system or machine. Typically, an embedded system is housed on a single

microprocessor board with the programs stored in ROM. Virtually all

appliances that have a digital Interface -- watches, microwaves, VCRs, cars --

utilize embedded systems. Some embedded systems include an operating

system, but many are so specialized that the entire logic can be implemented as

a single program. Embedded systems programming is the development of

programs intended to be part of a larger operating system or, in a somewhat

different usage, to be incorporated on a microprocessor that can then be

included as part of a variety of hardware devices. Several other definitions are:

A combination of computer hardware and software, and perhaps

additional mechanical or other parts, designed to perform a dedicated

function. In some cases, embedded systems are part of a larger system or

product, as in the case of an antilock braking system in a car. Contrast

with general-purpose computer.

A specialized computer system which is dedicated to a specific task.

Embedded systems range in size from a single processing board to

systems with operating systems (ex, Linux, Windows® NT Embedded).

Examples of embedded systems are medical equipment and

manufacturing equipment.

A computer system that is a component of a larger machine or system.

Embedded systems can respond to events in real time. Most digital

appliances, such as watches or cars, utilize an embedded system.

Hardware and software that forms a component of some larger system

and is expected to function without human intervention. Typically an

embedded system consists of a single-board microcomputer with

software in ROM, which starts running a dedicated application as soon

as power is turned on and does not stop until power is turned off.

An embedded system is some combination of computer hardware and

software, either fixed in capability or programmable, that is specifically

designed for a particular kind of application device. Industrial machines,

automobiles, medical equipment, cameras, household appliances,

airplanes, vending machines, and toys (as well as the more obvious

cellular phone and PDA) are among the myriad possible hosts of an

embedded system.

A phrase that refers to a device that contains computer logic on a chip

Inside it. Such equipment is electrical or battery powered. The chip

controls one or more functions of the equipment, such as remembering

how long it has been since the device last received maintenance,

An embedded system is a special-purpose computer system, which is

completely encapsulated by the device it controls. An embedded system

has specific requirements and performs pre-defined tasks, unlike a

general-purpose personal computer.

KIEL

Keil Software makes C compilers, macro assemblers, real-time kernels, debuggers, simulators, integrated environments, and evaluation boards for the 8051, 251, ARM, and XC16x/Cl6x/ST10 microcontroller families

Keil don’t make a compiler for every different microcontroller architecture. They concentrate on just a few chip families that they can support very well. That's why most of Keil's customers will agree that they have the best development tools for ARM, XC1 6x/C1 6x/ST1 0, 251 and 8051 microcontroller families. Since they have fewer product lines to support, Keil can dedicate more time to better supporting each tool chain. That allows them to improve their tools and product support faster than other vendors.

pVision3 IDE

pVision3, the new IDE from Keil Software, combines project management, make facilities, source code editing, program debugging, and complete simulation in one powerful environment, pVision3 helps you get programs working faster than ever while providing an easy-to-use development platform. The editor and debugger are integrated into a single application and provide a seamless embedded project development environment.

pVision3 provides unique features like

The Device Database which automatically sets the assembler, compiler, and linker options for the chip you select. This prevents you from wasting your time configuring the tools and helps you get started writing code faster.

A robust Project Manager which lets you create several different configurations of your target from a single project file. Only the Keil pVision3 IDE allows you to create an output file for simulating, an output file for debugging with an emulator, and an output file for programming an EPROM--all from the same Project file.

An integrated Make facility with automatic dependency generation. You don't have to figure out which header files and include files are used by which source files. The Keil compilers and assemblers do that automatically.

Interactive error correction. As your project compiles, errors and warnings appear in an output window. You may make corrections to the files in your project while pVision3 continues to compile in the background. Line numbers associated with each error or warning are automatically resynchronized when you make changes to the source.

Keil Software

pVision Debugger

The pVision Debugger from Keil supports simulation using only your PC or laptop, and debugging using your target system and a debugger interface. pVision includes traditional features like simple and complex breakpoints, watch windows, and execution control as well as sophisticated features like trace capture, execution profiler, code coverage, and logic analyzer. Viewing Code & Data

The pVision Debugger provides a number of ways to display variables and program objects.

Source Code Windows display your high-level language and assembly program source code.

The Disassembly Window shows mixed high-level language and assembly code.

The Registers Tab of the Project Workspace shows system registers.

The Symbol Window heir archly displays program symbols in your application.

The Output Window displays the output of various debugger commands.

The Memory Window displays up to four regions of code or data memory.

The Watch Window displays local variables, user-defined watch expression lists, and the call stack.

ExecutingpVision offers several ways you can control and manipulate program execution.

Reset - It is possible to debug reset conditions using the pVision Simulator.

Run/Stop - Buttons and Commands make starting and stopping program execution is easy.

Single-Stepping - pVision supports various methods of single-stepping through your target program.

Execution Trace - Execution trace information for each executed instruction is stored by pVision.

Breakpoints - Both simple and complex breakpoints are supported by the pVision Debugger.

Advanced Analysis Tools

Advanced analysis' tools are available to help you test and debug your embedded applications.

Code Coverage helps you determine how much of your program has been tested.

The Performance Analyser shows how functions and code blocks in your program perform.

The Execution Profiler shows execution counts and time for each line of code or instruction.

The Logic Analyser shows how various signals and variables in your program change over time.

Simulation

Simulation capabilities make it possible to test your target system without target hardware.

Instruction Simulation simulates the exact effects and timing of each IVICU instruction.

Interrupt Simulation simulates the cause and effect of a system or peripheral interrupt.

Peripheral Simulation simulates the effects of on-chip peripherals including special function registers.

Debugger Functions allow you to expand the command scope of the debugger and create and respond to stimuli.

Toolbox Buttons are a convenient way for you to connect debugger functions buttons on the user-interface.

Target Debugging Target debug drivers allow you to test programs running on target hardware.

JTAG Debugging uses external hardware to interface your PC to your target system.

A Target Monitor interfaces your PC to your target system using RS-232 and software.

Flash Programming uses a target interface to download your target program to Flash memory.

AGDl Drivers interface the Vision Debugger to third-party hardware or provide additional debugger features.

ABOUT C

As a programming language, C is rather like Pascal or Fortran. Values are stored in variables. Programs are structured by defining and calling functions. Program flow is controlled using loops, if statements and function calls. Input and output can be directed to the terminal or to files. Related data can be stored together in arrays or structures.

Of the three languages, C allows the most precise control of input and output. C is also rather more terse than Fortran or Pascal. This can result in short efficient programs, where the programmer has made wise use of C's range of powerful' operators. It also allows the programmer to produce programs, which are impossible to understand.

Programmers who are familiar with the use of pointers (or indirect addressing, to use the correct term) will welcome the ease of use compared with some other languages. Undisciplined use of pointers can lead to errors, which are very hard to trace. This course only deals with the simplest applications of pointers.

It is hoped that newcomers will find C a useful and friendly language. Care must be taken in using C. Many of the extra facilities, which it offers, can lead to extra types of programming error. You will have to learn to deal with these to successfully make the transition to being a C programmer.

C is a programming language developed at AT& T's Bell Laboratories of USA in 1972.

It was designed and written by a man named Dennis Ritche. In late seventies C begin to replace the more familiar languages of that time like ALGOL etc. Ritche seems to have been rather surprised that so many programmers preferred C to older languages like FORTRAN or PL/I or the newer like Pascal and APL. But, that's what happened.

STEPS IN LEARNING C

USAGE

C's primary use is for "system programming", including implementing operating systems and embedded system applications, due to a combination of desirable characteristics such as code portability and efficiency, ability to access specific hardware addresses, ability to "pun" types to , match externally imposed data access, requirements, and low runtime demand on system resources.

C has also been widely used to implement end-user applications, although as applications became larger much of that development shifted to other, higher level languages.

Alphabets,

digits, special

symbols

Constants,

variables,

keywords

Instructions Program

One consequence of C's wide acceptance and efficiency is that the compilers, libraries, and interpreters of other higher-level languages are often implemented in C.

C is used as an intermediate language by some higher-level languages.

"hello, world" example

The following simple application appeared in the first edition of K&R, and has become the model for an introductory program in most programming textbooks, regardless of programming language. The program prints out "hello, world" to the standard output, which is usually a terminal or screen display. Standard output might also be a file or some other- hardware device, depending on how standard output is mapped at the time the program is executed.

Main(){

printf(“hello, world\n”);}

The above program will compile on most modern compilers that are not in compliance mode, but does not meet the requirements of either C89 or C99. Compiling this program in C99 compliance mode will result in warning or error messages. 151 A compliant version of the above program follows:

#include <stdio.h> int main(void)

{printf(“hello, world\n”); return 0;

}

A Very Simple Program

This program which will print out the message This is a C program #include <stdio.h> main(){

printf(“This is a C program\n”);}

Though the program is very simple, a few points are worthy of note.

Every C program contains a function called main. This is the start point of the program.

#include <stdio.h> allows the program to interact with the screen, keyboard and file system of your computer. You will find it at the beginning of almost every C program.

Main() declares the start of the function, while the two curly brackets show the start and finish of the function. Curly brackets in C are used to group statements together as in a function, or in the body of a loop. Such a grouping is known as a compound statement or a block.

printf("This is a C program\n"); prints the words on the screen. The text to be printed is enclosed in double quotes. The \n at the end of the text tells the program to print a newline as part of the output.

Expressions and Operators

One reason for the power of C is its wide range of useful operators. An operator is a function which is applied to values to give a result. You should be familiar with operators such as+,-,/.

Arithmetic operators are the most common. Other operators are used for comparison of values, combination of logical states, and manipulation of individual binary digits. The binary operators are rather low level for so are not covered here,

Operators and values are combined to form expressions. The values produced by these expressions can be stored in variables, or used as a part of even larger expressions._______________________________________________________________

Assignment Statement

The easiest example of an expression is in the assignment statement. An expression is evaluated, and the result is saved in a variable. A simple example might look like

y = (m* X) + C

This assignment will save the value of the expression in variable y.

Arithmetic operators

Here are the most common arithmetic operators

+ Addition- Subtraction * Multiplication / Division % Modulo Reduction (Remainder from integer division)

*,/and % will be performed before + or - in any expression. Brackets can be used to force a different order of evaluation to this. Where division is performed between two integers, the result will be an integer, with remainder discarded. Modulo reduction is only meaningful between integers. If a program is ever required to divide a number by zero, this will cause an error, usually causing the program to crash.

Here is some arithmetic expressions used within assignment statements.

velocity = distance / time;

force = mass acceleration;

count = count + 1; C has some operators which allow abbreviation of certain types of arithmetic assignment statements.

Shorthand Equivalent

i++; or ++i; i = i + 1;i--; or --i; I = I – 1;

These operations are usually very efficient. They can be combined with another expression.

X = a * b++; is equivalent to x = a * b;x = b+ 1;

Versions where the operator occurs before the variable name change the value of the variable before evaluating the expression, so

x = --i * (a + b) ; is equivalent to i = i – 1;x = I * (a + b);

These can cause confusion if you try to do too many things on one command line. You are recommended to restrict your use of ++ and - to ensure that your programs stay readable.

Another shorthand notation is listed below

Shorthand Equivalent

i+ = 10; i = i + 10;i -= 10; i = i - 10;i *= 10; i = i * 10;i /= 10; i = i / 10;

These are simple to read and use.

Logical Connectors

These are the usual And, Or and Not operators.

Symbol Meaning

&& And II Or

! Not

They are frequently used to combine relational operators, for example

x < 20 && x >= 10 In C these logical connectives employ a technique known as lazy evaluation. They evaluate their left hand operand, and then only evaluate the right hand one if this is required. Clearly false && anything is always false, true 11 anything is always true. In such cases the second test is not evaluated.

Not operates on a single logical value, its effect is to reverse its state. Here is an example of its use.if ( ! acceptable)

printf(“Not Acceptable !!\n”);

Special Characters

The following special patterns are used to represent a single character in C programs. The leading backslash in the single quotes indicates that more information is to follow.

C code Meaning

’\014’’\n’’\t’’\\’’\”’\” ‘’\b’’\r’’\f’’\0’

Bit pattern for Form Feed New line Tab Backslash Single Quote Double Quote Backspace Carriage Return Form Feed NULL (String Terminator)

COMMANDS USED

1. SWITCH-CASE STATEMANT:The control statement that allows us to make a decision from the number of choices is called a switch, or switch case - default. Since these three keywords go together to make up the control statement.2. FOR LOOP:

For is the most popular looping instruction. It allows us to specify three things in a single line.

a) Setting loop counter to initial value

b) Testing the loop counter to determine whether its value has reached the no. of repetitions desired

c) Increasing the value of loop counter each time the program segment within the loop has been executed.

3. WHILE:A while loop is ideally suited for cases where we want to do something a fixed no. of times.

4. BREAK:We often come across situations where we want to jump out of a loop instantly, without waiting to get back to conditional test. The keyword break allows us to do this. When break is encountered inside any loop, control automatically passes to the first statement after the loop,

5. INPORT:Inport reads a word from a hardware portInportb reads a byte from a hardware port

6. OUTPORT:Outport outputs a word to a hardware portOutportb outputs a byte to a hardware port

INTRODUCTION TO ISP – FLASH PROGRAMMER

This ISP programmer can be used either for in system programming or as a stand – alone spi programmer for ATMEL programmable devices. The ISP 30a.zip file contains the main program and the o/p port driver. Place all files in same folder.

The main screen view of the program is shown in figure

Following are the main features of this software,Read and write the intel hex file read signature, lock and fuse bits clear and file memory buffer verify with memory buffer reload current hex file display buffer checksum program selected lock bits and fuses auto detection of hardware.

The software does not provide the erase command because this function is performed automatically during device programming. If you are required to erase the controller, first use the clear buffer command then program the controller, this will erase the controller and also set the AVR device fuses to default seting.

Internal architecture of the ISP is shown below: